The Who, What, Where, When and Sometimes, Why.

Birthweight

Studies show women with a higher birthweight (a woman’s weight when she was born) have an increased risk of breast cancer, especially before menopause [48-53].

A higher birthweight doesn’t appear to be linked to higher estrogen levels in adulthood [54-56]. However, birthweight may be a marker of factors related to growth that affect breast cancer risk (such as adult height) [55,57-58].

Other reasons behind a link between birthweight and breast cancer risk are under study.

Learn about other early life exposures and breast cancer risk

For a summary of research studies on birthweight and breast cancer risk, visit the Breast Cancer Research Studies section.

Updated 02/22/21